Cyanobacteria can produce extracellular polysaccharides (EPS) and release them to the environment, which is one of the adaptive mechanisms of cyanobacteria evolved to face complicated and variable environment. As a protective barrier between cell and environment, the EPS play a protective role against desiccation, ultraviolet radiation, biomineralization, or predation by protozoans. The EPS produced by cyanobacteria are a kind of complex anionic heteropolymer polysaccharides, more than 75% of which are composed of six or more monosaccharaides. Glucose is the most frequent kind of monosaccharaides. The characteristics of the EPS vary with cyanobacterial species. Most of the EPS show an anionic feature due to the charged groups, such as uronic acid and sulfate groups. Sulfate group is the basis of the anti-viral properties of polysaccharides, while hydrophobic groups such as ester-linked acetyl groups, peptides moieties, and deoxy sugars contribute to emulsifying properties. Therefore, the EPS produced by cyanobacteria have a broad application prospect in many industries, such as food additives, cosmetology, pharmacology, and wastewater treatment. The industrial application of the EPS can not only reuse the cyanobacteria bloom, bringing considerable economic benefits, but also provide a solution to the salvaging cyanobacteria distribution problem, avoiding its secondary pollution. Until now, there is no commodity from cyanobacterial EPS, and many technical problems are needed to be solved between the theoretical study and large batch industrial production.